1. Field of the Invention
This invention relates to methods for fabricating thin film magnetic write heads. More specifically, the invention relates to methods for fabricating a thin film write head for perpendicular recording having a bi-layer non-magnetic gap, wherein the outer layer is resistant to the caustic process conditions present in photo-resist development.
2. Description of the Related Art
As areal densities for magnetic storage media continue to increase, the critical dimensions for thin film write heads are driven to smaller levels. For future designs, write pole dimensions such as track widths (TW) and flare points (FP) will be on the order of 50 nm. Gap layers, which separate the magnetic pole from the shield structure, will shrink in thickness along with other pole dimensions. These thinner layers are increasingly susceptible to being etched or damaged by processing chemistry of the prior art. In particular, one common gap layer material in popular use is alumina. In very thin layers, this material is susceptible to being etched if exposed to standard photo-resist developer solutions which are generally caustic (pH>7) in nature. Problems can occur if an alumina gap layer is deposited over a pole layer, then subsequently masked with a conventional photo-resist. Damage to the alumina layer can occur during photo-resist development, compromising the subsequent performance of the write pole. These problems can be magnified if multiple photo-resist steps are carried out over the same alumina gap layer, as may occur in head production if a photo-resist layer is stripped and re-applied due to an imaging error. What is needed is a better process for making a perpendicular magnetic head that minimizes the sensitivity of non-magnetic gap layers to photo-resist processing.
FIG. 1 (Prior Art) is a partial, cross sectional view of a typical thin film perpendicular write head 100. The head comprises shield layers 102, 104, shaping layer 110, coil structure 108, main pole 112, lower return pole layer 106, wrap around shield 114, and upper return pole layer 116. Alternatively, structure 114 may also be a trailing shield. Details of wrap around shields and trailing shields, as applied to perpendicular recording heads, can be found in, for example, US Patent Application Publications 2007/0146930, 2007/0115584, 2006/0174474, 2006/0044682, and 2007/0137027.